This invention relates to an improved laminated padlock and in particular relates to an improved locking mechanism fixed in the lock body which simplifies the structure of the padlock components and consequentially reduces manufacturing costs in addition to ensuring its safe locking function.
Laminated padlocks previously provided are as shown in FIGS. 1 and 2, wherein the padlock 10 includes: a lock body 11 formed of a plurality of metal plates 111 with a central chamber formed therein; a key-operated lock barrel 12 having a tumbling portion 13 and an actuating push tab 121 installed in the central chamber of the lock body 11; a movable check bolt 14 matched with a spring 141 provided in the upper portion of the central chamber operated in relation to the push tab 121 of the key-operated lock barrel 12; and a U-shaped shackle 15 with a notch 151 at the shorter end slidingly provided in the lock body 11 with a spring 152 at the longer end thereof. The known padlock 10 is shown in its locked position in FIG. 1. When the key is inserted into the key-operated lock lock barrel 12 and turned to a certain angle as shown in FIGS. 3 and 4, the push tab 121 of the operating device 12 will drive the check bolt 14 to disengage with the notch 151 of the shackle 15 which is moved to an unlocked position through the expansion of the spring 152.
The major problem of the known padlock 10 is that, since the check bolt 14 has only a unilateral check function, the padlock 10 can be easily unlocked by an unauthorized person who happens to know the structure of the padlock 10 and the side wall of the padlock 10 with a hammer or the like in the direction as shown by the arrow in FIG. 1. On being punched in that direction, the check bolt 14 will be instantaneously moved away from the point of impact, and will be disengaged with the notch 151 of the shackle 15, and the padlock 10 is rendered unlocked even without the key.
Shown in FIG. 5 is an improved laminated padlock patented in the United States under U.S. Pat. No. 3,979,931 issued to Tsui Wai Man. The improved padlock 20 as shown includes: a padlock body 21 also made of a plurality of metal plates 211 with a central chamber and some openings formed therein; a lock barrel 22 having a tumbling portion 23 at one side and a pair of cam tabs 221 at the upper end thereof installed in the central chamber; a pair of movable lock plates 24 mounted in a side-by-side relationship within the upper room of the central chamber of the lock body 21 in connection with the cam tabs 221; and a U-shaped shackle 25 having a pair of notches 251 formed in the heel and toe portions slidingly disposed in the openings of the lock body 21 with a spring 251 situated at the heel end.
The structure of the lock plates 24 is shown in FIGS. 6 and 7, wherein the lock plates 24 each include elongated shafts 241,242 which carry at opposite ends detents 2412,2422 for locking engagement with respective notches 251 when the shackle 25 is pressed inward, and at the other opposite ends extending arms 2411,2421 for being operated by the cam tabs 221 of the lock barrel 22, and a pair of springs 243 provided between the two lock plates 24 through a pair of guide pins 244 mounted between the extending arms 2411,2421 and the back side of the detents 2412,2422 in separate hollows 2413,2423 formed therein. The combined lock plates 24 are placed in the upper chamber defined by a housing B of five metal plates 111 as shown in FIG. 8, where the lower metal plate B1 is secured thereunder, defining an S-shaped opening 245 for engagement by the cam tabs 221 with respect to the extending arms 2411,2421. When the key is inserted into the lock barrel and turned to a certain angle as shown in FIG. 10, the two cam tabs 221 will respectively push the extending arms 2411,2421 backward therefrom, moving the lock plates 24 inward to retract the detents 2412,2422 from the notches 251. The spring 252 then acts to force the shackle 25 outward and unlocks the lock.
What the second known padlock shown in FIG. 5 has improved is the double lock arrangement for protecting it from being unlocked by any unauthorized person through the aforesaid hammering method. However, owing to the complicated structure of the lock plates, much room is still left to be improved.